[python-fastapi] add useExternalImplementationPackage to reference an external absolue impl package

docs/generators/python-fastapi.md

@@ -32,6 +32,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
 |sourceFolder|directory for generated python source code| |src|
+|useExternalImplementationPackage|If true, fastapiImplementationPackage is a fully qualified python package that already exists outside the generated package: it is imported as-is (not prefixed with packageName) and its __init__.py is not generated.| |false|
 
 ## IMPORT MAPPING
 

modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenConstants.java

@@ -472,6 +472,9 @@ public static enum ENUM_PROPERTY_NAMING_TYPE {camelCase, PascalCase, snake_case,
 
     public static final String FASTAPI_IMPLEMENTATION_PACKAGE = "fastapiImplementationPackage";
 
+    public static final String USE_EXTERNAL_IMPLEMENTATION_PACKAGE = "useExternalImplementationPackage";
+    public static final String USE_EXTERNAL_IMPLEMENTATION_PACKAGE_DESC = "If true, fastapiImplementationPackage is a fully qualified python package that already exists outside the generated package: it is imported as-is (not prefixed with packageName) and its __init__.py is not generated.";
+
     public static final String WITH_XML = "withXml";
 
     public static final String WITH_GO_MOD = "withGoMod";

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonFastAPIServerCodegen.java

@@ -63,6 +63,7 @@ public class PythonFastAPIServerCodegen extends AbstractPythonCodegen {
     private static final String X_FASTAPI_REQUEST_BODY_EXAMPLE = "x-python-fastapi-request-body-example";
 
     private String implPackage;
+    private boolean useExternalImplementationPackage = false;
 
     @Override
     public CodegenType getTag() {
@@ -128,6 +129,8 @@ public PythonFastAPIServerCodegen() {
                 .defaultValue(DEFAULT_SOURCE_FOLDER));
         cliOptions.add(new CliOption(CodegenConstants.FASTAPI_IMPLEMENTATION_PACKAGE, "python package name for the implementation code (convention: snake_case).")
                 .defaultValue(implPackage));
+        cliOptions.add(CliOption.newBoolean(CodegenConstants.USE_EXTERNAL_IMPLEMENTATION_PACKAGE, CodegenConstants.USE_EXTERNAL_IMPLEMENTATION_PACKAGE_DESC)
+                .defaultValue(Boolean.FALSE.toString()));
     }
 
     @Override
@@ -172,16 +175,22 @@ public void processOpts() {
             this.sourceFolder = ((String) additionalProperties.get(CodegenConstants.SOURCE_FOLDER));
         }
 
+        if (additionalProperties.containsKey(CodegenConstants.USE_EXTERNAL_IMPLEMENTATION_PACKAGE)) {
+            this.useExternalImplementationPackage = convertPropertyToBooleanAndWriteBack(CodegenConstants.USE_EXTERNAL_IMPLEMENTATION_PACKAGE);
+        }
+
         if (additionalProperties.containsKey(CodegenConstants.FASTAPI_IMPLEMENTATION_PACKAGE)) {
             this.implPackage = ((String) additionalProperties.get(CodegenConstants.FASTAPI_IMPLEMENTATION_PACKAGE));
-            // Prefix templating value with the package name
-            additionalProperties.put(CodegenConstants.FASTAPI_IMPLEMENTATION_PACKAGE,
-                    this.packageName + "." + this.implPackage);
         }
 
         modelPackage = packageName + "." + modelPackage;
         apiPackage = packageName + "." + apiPackage;
-        implPackage = packageName + "." + implPackage;
+        if (!useExternalImplementationPackage) {
+            // The implementation package is a sub-package of the generated one
+            implPackage = packageName + "." + implPackage;
+        }
+        // Templating value: the fully qualified implementation package
+        additionalProperties.put(CodegenConstants.FASTAPI_IMPLEMENTATION_PACKAGE, implPackage);
 
         supportingFiles.add(new SupportingFile("README.mustache", "", "README.md"));
         supportingFiles.add(new SupportingFile("openapi.mustache", "", "openapi.yaml"));
@@ -200,7 +209,10 @@ public void processOpts() {
         }
         supportingFiles.add(new SupportingFile("__init__.mustache", StringUtils.substringAfter(modelFileFolder(), outputFolder), "__init__.py"));
         supportingFiles.add(new SupportingFile("__init__.mustache", StringUtils.substringAfter(apiFileFolder(), outputFolder), "__init__.py"));
-        supportingFiles.add(new SupportingFile("__init__.mustache", StringUtils.substringAfter(apiImplFileFolder(), outputFolder), "__init__.py"));
+        if (!useExternalImplementationPackage) {
+            // An external implementation package already exists and is owned by the user: nothing to generate in it
+            supportingFiles.add(new SupportingFile("__init__.mustache", StringUtils.substringAfter(apiImplFileFolder(), outputFolder), "__init__.py"));
+        }
 
         supportingFiles.add(new SupportingFile("conftest.mustache", testPackage.replace('.', File.separatorChar), "conftest.py"));
 

modules/openapi-generator/src/test/java/org/openapitools/codegen/python/PythonFastapiCodegenTest.java

@@ -31,6 +31,39 @@ public void testAdditionalPropertiesPutForConfigValues() throws Exception {
         files.forEach(File::deleteOnExit);
 
         TestUtils.assertFileExists(Paths.get(output.getAbsolutePath(), "/src", "/nodesc", IMPL_PKG, "__init__.py"));
+        TestUtils.assertFileContains(Paths.get(output + "/src/nodesc/apis/nodesc_api.py"),
+                "import nodesc." + IMPL_PKG + "\n");
+    }
+
+    @Test
+    public void testExternalImplementationPackage() throws Exception {
+        File output = Files.createTempDirectory("test").toFile();
+        output.deleteOnExit();
+
+        // A fully qualified package living outside the generated one, owned by the user
+        final String EXTERNAL_IMPL_PKG = "my_company.handlers";
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName("python-fastapi")
+                .setPackageName("nodesc")
+                .setOutputDir(output.getAbsolutePath().replace("\\", "/"))
+                .setInputSpec("src/test/resources/3_1/nodesc.yaml")
+                .addAdditionalProperty(CodegenConstants.FASTAPI_IMPLEMENTATION_PACKAGE, EXTERNAL_IMPL_PKG)
+                .addAdditionalProperty(CodegenConstants.USE_EXTERNAL_IMPLEMENTATION_PACKAGE, true);
+
+        DefaultGenerator generator = new DefaultGenerator();
+        List<File> files = generator.opts(configurator.toClientOptInput()).generate();
+        files.forEach(File::deleteOnExit);
+
+        // Imported as-is, not prefixed with the package name
+        final String apiFile = output + "/src/nodesc/apis/nodesc_api.py";
+        TestUtils.assertFileContains(Paths.get(apiFile), "import " + EXTERNAL_IMPL_PKG + "\n");
+        TestUtils.assertFileContains(Paths.get(apiFile), "ns_pkg = " + EXTERNAL_IMPL_PKG + "\n");
+        TestUtils.assertFileNotContains(Paths.get(apiFile), "nodesc." + EXTERNAL_IMPL_PKG);
+
+        // Nothing is generated in a package the generator does not own
+        TestUtils.assertFileNotExists(Paths.get(output.getAbsolutePath(), "/src", "/nodesc", "impl", "__init__.py"));
+        TestUtils.assertFileNotExists(Paths.get(output.getAbsolutePath(), "/src", "/my_company", "/handlers", "__init__.py"));
+        TestUtils.assertFileNotExists(Paths.get(output.getAbsolutePath(), "/src", "/nodesc", "/my_company", "/handlers", "__init__.py"));
     }
 
     @Test